1. Field of the Invention
The present invention relates to a plasma display apparatus, and more particularly to a plasma display apparatus in which bus electrodes respectively have a predetermined thickness so as to easily generate a plasma discharge between the bus electrodes opposite to each other, or the bus electrodes respectively protrude toward discharge spaces to form at least two electrode layers.
2. Description of the Background Art
In general, in a plasma display apparatus, a barrier rib formed between an upper glass substrate and a lower glass substrate forms one unit cell. Each cell is filled with an inert gas such as He—Ne or He—Xe. When the inert gas is discharged in response to a high frequency voltage, vacuum ultraviolet rays are generated, and phosphors formed between the barrier ribs are excited to implement images. The plasma display apparatus is widely used as a next generation display device because the plasma display apparatus can be easily manufactured due to the simple structure and has advantages of thinner structure and low power consumption.
FIG. 1 is a cross-sectional view illustrating the structure of a conventional ITO-less plasma display apparatus. FIG. 1 shows a discharge cell of a plasma display apparatus of which upper substrate is rotated by an angle of 90 degree.
In general, since the conventional plasma display apparatus displays images while visible rays generated from the phosphors pass through the upper substrate, a scan electrode and a sustain electrode formed on the upper substrate are formed as a transparent electrode. The transparent electrode has a transparent property so that the visible rays can be transmitted through, and is usually comprised of Indium Tin Oxide (ITO) and tin oxide (SnO2).
However, a bus electrode is used together with the transparent electrode since the transparent electrode has a large resistance.
In this structure, an ITO patterning process is essentially required so as to improve beam permeability, and the ITO patterning process greatly affect the efficiency of the plasma discharge. However, the efficiency and characteristics of the plasma discharge may be deteriorated when the ITO is misaligned and the ITO is cut off. The competitive price of the Plasma Display Panel (PDP) is reduced because labor costs and the cost of materials increase due to the use of the ITO.
Thus, an ITO-less method in which the ITO patterning process is omitted has been developed, and the structure of the ITO-less plasma display apparatus with reference to FIG. 1.
Referring to FIG. 1, a pair of scan electrodes 11 and sustain electrode 12 are formed on an upper glass substrate 10 and an address electrode 21 is formed on a lower glass substrate 20 to cross the scan electrode 11 and the sustain electrode 12.
The scan electrode 11 and the sustain electrode 12 is comprised of a metal electrode i.e. a bus electrode.
An upper dielectric layer 13 is formed on the upper substrate 10 on which the scan electrode 11 and the sustain electrode 12 are formed, to cover the scan electrode 11 and the sustain electrode 12. A protection layer 14 is formed on the upper dielectric layer 13 so as to prevent the upper dielectric layer 13 the scan electrode 11 and the sustain electrode 12 from being damaged by sputtering generated during the discharge of plasma. Magnesium oxide (MgO) is generally used as the protection layer 14.
A lower dielectric layer 23 is formed on the lower substrate 20 to cover the address electrode 21 and a barrier rib 22 is formed on the lower dielectric layer 23. Discharge cells are divided each other by the barrier rib 22. An Red (R), Green (G) and Blue (B) phosphors 24 is coated on the discharge cell.
In the conventional ITO-less plasma display apparatus, a discharge voltage has to increase since a discharge gap between the bus electrodes increases due to the non-existence of the ITO electrode. In this case, the efficiency of the plasma discharge is reduced according as the discharge voltage increases.
In order to solve above problem, there has been developed a technique for increasing the efficiency of the plasma discharge by reducing the discharge gap between the bus electrodes. FIG. 2 shows an example of the structure of electrodes in a conventional ITO-less plasma display apparatus. Referring to FIG. 2, a plurality of bus electrodes is formed in parallel each other in a horizontal direction on each of the scan electrodes 11 and the sustain electrodes 12 so as to increase the efficiency of the plasma discharge. However, an aperture ratio decreases since the bus electrodes are arranged in the horizontal direction. Thus, the beam permeability of the visible rays generated from the phosphors is reduced, and luminance of the plasma display apparatus decreases. The efficiency of the plasma discharge is low since the discharge between the bus electrodes is a surface discharge through the upper dielectric layer 13 of FIG. 1 that covers the bus electrodes.